The present invention relates to a novel process for amorphous atorvastatin which is known by the chemical name [R--(R*,R*)]-2-(4-fluorophenyl)-.beta.,.delta.-dihydroxy-5-(1-methylethyl) -3-phenyl-4-[(phenylamino) carbonyl]-1H-pyrrole-1-heptanoic acid hemi calcium salt which is useful as a pharmaceutical agent. Atorvastatin is useful as an inhibitor of the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-COA reductase) and is thus useful as a hypolipidemic and hypocholesterolemic agent.
U.S. Pat. No. 4,681,893, which is herein incorporated by reference, discloses certain trans-6-[2-(3- or 4-carboxamido-substituted-pyrrol-1- yl)alkyl]-4-hydroxy-pyran-2-ones including trans (.+-.)-5- (4-fluorophenyl)-2-(1-methylethyl)-N,4-diphenyl-1-[(2-tetrahydro-4-hydroxy -6-oxo-2H-pyran-2-yl)ethyl]-1H-pyrrole-3-carboxamide.
U.S. Pat. No. 5,273,995, which is herein incorporated by reference, discloses the enantiomer having the R form of the ring-opened acid of trans-5-(4-fluorophenyl)-2-(1-methylethyl)-N,4-diphenyl-1-[(2-tetrahydro-4 -hydroxy-6-oxo-2H-pyran-2-yl)ethyl]-1H-pyrrole-3-carboxamide, i.e., [R--(R*,R*)]-2-(4-fluorophenyl)-.beta.,.delta.-dihydroxy-5-(1-methylethyl) -3-phenyl-4-[(phenylamino)carbonyl]-1H-pyrrole-1-heptanoic acid.
U.S. Pat. Nos. 5,003,080; 5,097,045; 5,103,024; 5,124,482; 5,149,837; 5,155,251; 5,216,174; 5,245,047; 5,248,793; 5,280,126; 5,397,792; and 5,342,952, which are herein incorporated by reference, disclose various processes and key intermediates for preparing atorvastatin.
Atorvastatin is prepared as its calcium salt, i.e., [R--(R*,R*)]-2-(4-fluorophenyl)-.beta.,.delta.-dihydroxy-5-(1-methylethyl) -3-phenyl-4-[(phenylamino)carbonyl]-1H-pyrrole-1-heptanoic acid calcium salt (2:1). The calcium salt is desirable since it enables atorvastatin to be conveniently formulated in, for example, tablets, capsules, lozenges, powders, and the like for oral administration.
Concurrently filed U.S. patent applications titled "Crystalline [R--(R*,R*)]-2-(4-fluorophenyl)-.beta.,.delta.-dihydroxy-5-(1-methylethyl) -3-phenyl-4-[(phenylamino)carbonyl]-1H-pyrrole-1-heptanoic Acid Calcium Salt (2:1)"and" Form III Crystalline [R--(R*,R*)]-2-(4-fluorophenyl)-.beta.,.delta.-dihydroxy-5-(1-methylethyl) -3-phenyl-4-[(phenylamino)carbonyl]-1H-pyrrole-1-heptanoic Acid Calcium Salt (2:1)" commonly owned, Ser. No. 08/945,812 now U.S. Pat. No. 5,969,156, and, Ser. No. 08/945,817, abandoned, disclose atorvastatin in various new crystalline forms designated Form I, Form II, Form III, and Form IV.
Atorvastatin disclosed in the above United States Patents is an amorphous solid. We have found that after the advent of crystalline atorvastatin, the production of amorphous atorvastatin by the previously disclosed processes was not consistently reproducible.
It has been disclosed that the amorphous forms in a number of drugs exhibit different dissolution characteristics and in some cases different bioavailability patterns compared to the crystalline form (Konno T., Chem. Pharm. Bull., 1990;38:2003-2007). For some therapeutic indications one bioavailability pattern may be favored over another. Therefore, it is desirable to have a procedure for converting the crystalline form of a drug to the amorphous form.
The object of the present invention is a process which is amenable to large-scale production for converting crystalline Form I atorvastatin into amorphous atorvastatin.
We have surprisingly and unexpectedly found that solutions of atorvastatin in a non-hydroxylic solvent afford, after removal of the solvent, amorphous atorvastatin.